Intragenomic diversity and geographical adaptability of diploid cotton species revealed by cytogenetic studies

Cotton is one of the most important crops in Iran, and is cultivated in different regions of the country. Gossypium herbaceum is one of the A-genome cottons, which is a potentially important genetic resource for cotton breeding programs. Collecting native cultivars of this species growing in different regions is a vital step in broadening variability of the gene pool. The G. herbaceum is one of the two cultivated species under cultivation in Iran, which is specifically adapted to a given environment and includes more than 40 ecotypes, named as landrace cottons. The present paper reports the intragenomic characteristics analysis of 42 G. herbaceum cultivars in the cotton genebank using cytological methods. The karyological studies showed variations within the species in the size of chromosome, chromosome volume and karyotype formulae. All cultivars possessed 2n=26 chromosome, but varied with regard to number of SAT-chromosomes (ranging from 1 to 3) and the chromosomes carrying secondary constructions. Karyotypes were of symmetrical type, having small chromosomes. Analysis of variance revealed significant differences between the cultivars as well as the chromosomes. Cluster analysis could group the cultivars in four distinct clusters. The present study indicates genomic differences among diploid G. herbaceum cultivars, which can be used in cotton hybridization programs in Iran or other countries.